Magnetic wire recording



Dec. 11, 1951 T. M. SHRADER MAGNETIC WIRE RECORDING Filed Jan. 31 1947 Wmm ATTORNEY Patented Dec. 11, 1951 UNITED PATENT" OFF ICE.

2;,7s,02 a M G IC WIRE REQQRDmG Ierry-M. Shu der; Qa s J1, ass snq to a io C rporat on oi Am c rpo a i of De a- Application J anuary'31, 194%, Serial No. 725,559 lQ aiPs -r. 3: 47 4 My pr sen i ventionrelates to impr vements telegr-aphones. of the typ employing; magnetic; wire records, and has; for its principal? object to. provide an improved reeling system including a Wire-record that will not, roll- (about. its lone axis) in its travel between the reels, whereby the same circumferential section of the wire, will always be presented to the sound-head of the recording and/or reproducingmachine.

The achievement of the foregoing principal ob.-. i-ect' of my invention permits. me. tov provide 1011: gltudinallyemagnetized wire-recordings of sub: stantially constant. fidelity, and this. too without the necessity of employing an apertured polepiece. assembly orother orificed "pick-up" through which the wire must. be threaded.

Alternatively, my present invention permits me to, magnetize the wire in the transverse direction and thereby to achieve the low recordin and play-back speeds heretofore practical only with tape-records. In this connection it will be re: calledthat previous attempts to. achievea trans: verselyemagnetized-wire recording system have invariably involved the use of a multiplicity ofmagnetic-pole-pieces arranged in circular array about a common point in the path of the wire and a phase-shifting network or other balancing system for handlingthe. signal-energy picked-up by the several discrete pole-pieces. (That such prior-art systems are impractical will beapparent when one appreciates the degree of precision that would be required to. make and to install such a pole-piece assembly about a wire. that is only a few thousandthsof an inch in diameter.)-

The non-rolling wire-record and the reeling the same wire when not set, or straight.- I- ofcourse appreciate. that most any wire will ace quire a set when wound upon a supply spool or after repeated excursions about a reeling system or other curved path, but I have ascertained that the nature and orientation of the set thus nor-e.

-ma lly acquired is of no useful significance solvingthe problems with which I: am

Thus, my invention may be said to res de, .atleast part, in discovering the degree and orientation of set required to prevents. wirefrom roll;

2 ing and in the application of this discoverytil. the art or magnetic-wire recording. My inyention may be said further to, reside the proyi; sion of a reeling system wherein the factors at reel-and-pulley design which tend to cause a, moving wire -to roll are eliminated and, further, in the provision of a simple, inexpensive and con: verientmeth d f n w an unw und W re.v a pr vi usly W und w e or a p s n ly-wound wirewi h he set required to m miz ollin a reelin system of any par ic lar size or som plexity.

My invention will be described connection with the accompanying drawing wherein:

Fig. l is a diagrammatic view of a winding sys: tem showing one manner of endowing a Pl i ie. ously-wound magnetic-wire with a circular set of the orientation and degree required in the practice of my invention;

Fig. 2.- is a View perspective of a, reel assem;

bly showing a preferred way ofendowing a press ently-wound magnetic-wire record=blank with a circularset, i accordance with my invention;

Fig. 3 is an enlarged fragmentary view or one of the pulleys or rollers of Fig. 2 showing the im: proved conformation of the wire-receiving grooves, as dictated by my present invention;

Fig. 4 is an enlarged elevational view of one form of sound-head which may be utilized in longitudinally recording signals upon a magnetic wireerecord, and

Fig. 5 is a similar view of a. soundehead haying twohoppositely located pole-nieces for mastic: tizing a non-rolling wire transversely.

Referring to Fig. 1: In carryin my invention into eiiect I may impart. a circularrset to the magnetic-wire W by running it, preferably un: der slight tension, around a thin rod, cylinder or roller R. When received from the manufac: turer the wire will usually exhibit a, spiral set by reason of its being wrapped around and along thecore of a shippingspool ,8. Such a splroll; wound-wire will roll while beingunwound I find that if I- impart. a circular set to. thewlre while it is subject to rolling, the molecular forces which give rise to this movement. will be stored in the wire and cause it toroll at some future time. I find that the. rollingmovement incident to. unwindin the. wire from its shippingspool can largely be. dissipated byproviding guide rollers Giand Glen opposite sides; ofthe Wa one ormdr I r a l e era f om he o n er which the re l e t u spool S. i also make sure that the wire runs over the rollers 61., R, G? and onto the telee graphones storage reel I in the same direction that it was originally wound upon its shipping spool S. Thus, as shown in Fig. 1, when the wire is wound counter-clockwise on the spool S, I run it over the said rollers and onto the storage reel l in the same (counter-clockwise) direction. This also helps in avoiding setting-up molecular stresses in the wire which would cause it to roll and, further, prolongs the life of the circular set which the wire acquires in being run over the setting-roller or rod R. Another roll-preventing precaution which I observe in winding the wire upon the telegraphone-reel l is to make sure that the wire approaches this reel in substantially the same plane as the one in which it is to be received on the said reel. (Since modern telegraphone-reels are usually very narrow, reel I may be considered to comprise but a single plane, in which case the wire may be said toleave the guide roller G in the plane of the reel I.)

Instead of imparting the circular set to the magnetic-wire before it is wound upon its storage reel, I may set the wire after it has been installed upon the reeling-system in which it is 4 to be used. Thus, as shown in Fig. 2, wherein the magnetic-wire record will be understood to be maintained under tension by oppositely biased coil springs C within the separate reels l and 2, I simply insert the rod R in back" of the wire, say at a point between the driving rollers 4 and 5, and then pull the wire away from the said rollers and run it at least once, from end-to-end, around the said rod. In the drawing the temporary path of the wire around the rod R is shown in broken lines, its permanent path is indicated by arrows.

As previously set forth my invention resides, in part, in the provision of a reeling system which will not itself impart a rolling movement to the magnetic-wire record. Such a reeling system is shown in Figs. 2 and 3.

The reelin system here shown is similar in many respects to the one claimed in my copending application Ser. No. 628,295 (RCV 10337), now Patent No. 2,557,012, issued June 12, 1951, and comprises a storage reel I and a take-up reel 2 mounted for independent rotation, in either direction, about a common axis or shaft 9 and two driving rollers 4 and 5 which are mounted in spaced relation for rotation about separate axes or shaft 6 and 1, respectively, parallel to the reel shaft 3. The magnetic-wire record, which is here designated 9, is wound to run between the storage reel l and the takeup reel 2 over the driving rollers 4 and 5 in paths tangent to the reels and rollers. The driving rollers 4 and 5 are each provided with a number of grooves 4a, 4b, 40, 5a, etc. (later described) within certain ones of which the wire is received, and with a circular flange 4f, 5f, respectively, to which a driving force is applied by a rubbertired wheel, not here shown. The arrangement of the rollers 4, 5 and the spacing of the grooves therein is preferably such that one groove on each roller is in register with the particular reel groove to which, or from which, the wire 9 is led. Thus, in the instant case groove 4a on roller 4 is in register with, or in substantially the same plane as, the mid-plane of the storage reel I, and groove 5c on-roller 5 is in register with the mid-plane of the groove in the takeup reel 2. The "spacing between the rollers per se should be wide enough to accommodate the sound-head II (which, as shown in Fig. 4, may

be similar to the one described in copending application Ser. No. 591,071 to Henry E. Roys, RCV 9965, now Patent No. 2,469,444, issued May 10, 1949). The spacing between the rollers and the reels will ordinarily be determined by the space available in the casing or other housing in which the reel assembly is contained. The reeling system, above described, differs from the ones shown in my above identified earlier filed case in two respects (a) in the instant case the direction of curvature oi the path of the wire is uniform throughout the reeling system and (b) in the shape of the grooves 4a, 5a, etc. in the driving rollers 4 and 5.

The first mentioned feature (a) is achieved by so placing the sound-head ll between the rollers 4 and 5 that it faces outwardly" whereby the wire 9 is urged outwardly and is caused to traverse an arc whose radius extends in the same direction as the radii of the other curves in the system. Thus, it will be observed upon inspection of Fig. 2 that all of the curves in the path of the wire in this reeling system are to the right, 'as viewed by an observer looking in the direction in which the wire is traveling. The importance of this feature of my invention will be apparent when it is appreciated that if the circularly-set magnetic wire 9 were obliged to traverse a reverse-bend the set in the wire might become completely ironed-out" or its radius of curvature increased beyond the limits, hereinafter prescribed. (In my earlier filed case the pressure exerted by the sound-head II on the wire 9 may result in reverse-curve which. if of a very large radius of curvature would not re-. move a circular set.)

As indicated at b, above, another important feature of my present invention resides in the shape of the grooves 4a, 4b, 4c, 5a, etc. in the driving rollers 4 and 5. I have found that the wire 9 is least likely to roll when, as shown in Fig. 3, the grooves have a flat bottom a: and flat sides 11,! and 2 which slant oif each at an angle of substantially 22.5 with respect to a line or plane normal to the axis of rotation of the rollers.

It has been my experience that rolling is most likely to occur when the wire is subjected to a reciprocating movement (as in my copending application Ser. No. 697,590 RCV 11147, now Patent No. 2,526,051 issued October 17, 1950), or is caused to set-up (or down) from a groove in one roller to a higher (or lower) groove in another roller and that the tendency of the wire to roll is most pronounced when the grooves have parallel sides and a curved bottom. In this latter connection I have observed that when a wire enters a round-bottomed groove at an angle with respect to the plane of the groove it does not ride on the center line of the groove but off-center above the bottom of the groove. As the wire advances in a round-bottom groove it rolls downwardly and inwardly to assume a position on the center line of the groove, from whence it passes to the next roller or reel. By making the bottom of the grooves flat as indicated at a: (Fig. 3), instead of curved, it becomes immaterial what position the wire occupies in the groove, since all points on the fiat bottom are equally distant from the axis of the roller. As a result the wire will not roll, irrespective of the position at which the wire enters or leaves the flat-bottom of the groove.-

I have also found that a V-shape groove when perfectly clean will tendto prevent rolling but ,1

do not recommend the use of such grooves in magnetic-wire recorders because dust and dirt accumulate in the bottom of the V and introduce eccentricities which give rise to a jerking movement. Furthermore, any irregularities in the surface of the wire or of the groove, due to wear, may cause the wire to shift its position with respect to the axis of rotation of the roller.

The flat outwardly-inclined side walls y and a of the fiat-bottomed grooves in the rollers 4 and 5 are designed to present the largest possible radius (r Fig. 3) of curvature to the wire 9 upon entering the rollers at a small angle. The 22.5 slant of these surfaces 11 and a is the optimum degree of slant when the diameter of the rollers 4 and 5 is substantially one inch, and the angle at which the wire enters the grove is substantially no greater than 5. Larger rollers, or an angle of approach greater than 5, will dictate a slant of more than 22.5 (but ordinarily not more than 45) for the side walls y and a of the said grooves.

While, as above indicated, the tendency of the magnetic-wire to roll is greatly decreased by the use of fiat-bottomed roller-grooves I relay upon the circular set of the wire to eliminate rolling. The radius of curvature of the circular set dictated by my invention is by no means critical. However, in determining the radius of curvature of the circular set with which a particular magnetic wire record is to be endowed, the following general rules must be observed. First, the radius of curvature of the set should be no smaller than the radius of curvature of the smallest curve about which that particular (e. g. solid or plated iron) magnedc-wire can run without loosing its magnetism. Since it can be assumed that even the most compact telegraphone reelingsystem will not contain such a curve, this first rule, in practice, means that the radius of curvature of the circular set should be no smaller than the radius of curvature of the smallest radius of curvature of the largest reel, roller, or pulley, in the reeling system. (In this connection I note that reeling system for iron-coated brass wire may contain smaller curvesthan those designed to handle solid-iron wire.)

With the foregoing parameters in mind and having regard to the elastic limit (or limits) of the wire I find it desirable to provide the wire, originally, with a circular set of a radius of curvature substantially mid-way between the radii of curvature of the smallest roller and the largest reel of the system, so that the stresses to which the wire is subjected are about equal in traversing both curves. As a practical matter a circular set of a satisfactory radius of curvature can usually be achieved by running the wire once around a 0.25 inch roller or rod (R, Figs. 1 and 2) under very slight tension. The magnetic properties of the wire are not permanently affected by running the wire around such a small curve since the circular set which the wire actually acquires in being run there around is of a radius of curvature lar er than that of the said small curve.

The advantages of my invention are manifest in so-called longitudinally-magnetized wire-systems by the highly constant acoustic fidelity of the recordings. Thus, whereas longitudinal recordings made on various present-day wire recorders of a musical note of fixed frequency (in this case 4000 cycles per second) exhibited a variation of from 6 to 12 decibels, the same note recorded in accordance with my present invention exhibited a variation of but one-half decibel, or even less. I attribute this improved performance to the fact of the applicator or sound head H.

the record 9 is played back in a machine where the longitudinally-magnetized wire may roll, a diiferent and perhaps totally unmagnetized surface section of the wire may be presented to the pole pieces of the pick-up device. (I intend the term longi;udinally-magnetized wire as used herein to include any magnetic-recording wherein the magnetic lines of force extend, generally, along the axis of the wire, though a transverse component may be present; for example as in the obliquely magnetized wire-records of Pederson and Paulson U. S. P. 873,078.)

The substantially complete absence of rolling permits me to impress the signal energy upon a wire record in the transverse direction and thus to achieve the low recording and play-back speeds heretofore practical only with transversely-magnetized tape-records. In this case, referring now to Fig. 5 I mount the magnetic -pole pieces N and S of the applicator or sound-head on opposite sides of the wire 9 along a common axis normal to the direction of movement of the wire.

I claim as my invention:

A telegraphone comprising, in combination, a reeling system including a storage reel and a take-up reel, said reels being the opposite ends of a path along which a flexible magnetic-wire record is adapted to run, a sound head, a first guide roller intermediate said storage reel and said sound head, a second guide roller intermediate said take-up reel and said sound head, said rollers being substantially one inch in diameter, and a flexible magnetic wire record wound to run between said reels around said rollers along said path, said wire record having a preformed circular set of a radius of curvature smaller than the largest radius of curvature of either of said reels but larger than that which would effect demagnetization of said wire when previously magnetized, the curves in said path being all in the same direction of movement of said wire, each of said rollers having a wire receiving groove the bottom of which is flat and parallel to the axis of rotation of said roller and the side walls of which are fiat and slant at an angle of approximately 22.5 degrees with respect to a plane normal to said axis, said wire moving along said path at points in proximhy to each of said rollers at a small angle to said plane, said small angle being not more ,than five degrees.

TERRY M. SHRADER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,858,553 Lignori May 17, 1932 2,089,287 Molloy Aug. 10, 1937 2,195,859 Gent Apr. 2, 1940 2,229,293 Huntley et a1. Jan. 21, 1941 2,251,322 Buhrendorf Aug. 5, 1941 2,265,246 Ott Dec. 9, 1941 2,369,017 Camras Feb. 6, 1945 2,372,810 Camras Apr. 3, 1945 2,409,942 Knapp Oct. 22, 1946 2,418,543 Camras Apr. 8, 1947 2,475,694 Camras July 12, 1949 

